/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.function.server;

import java.net.URI;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.function.Consumer;

import reactor.core.publisher.Mono;

import org.springframework.http.CacheControl;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseCookie;
import org.springframework.http.codec.HttpMessageWriter;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.util.Assert;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyInserter;
import org.springframework.web.server.ServerWebExchange;

/**
 * Default {@link EntityResponse.Builder} implementation.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 5.0
 */
class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T> {

    private final T entity;

    private final BodyInserter<T, ? super ServerHttpResponse> inserter;

    private int status = HttpStatus.OK.value();

    private final HttpHeaders headers = new HttpHeaders();

    private final MultiValueMap<String, ResponseCookie> cookies = new LinkedMultiValueMap<>();

    private final Map<String, Object> hints = new HashMap<>();


    public DefaultEntityResponseBuilder(T entity, BodyInserter<T, ? super ServerHttpResponse> inserter) {
        this.entity = entity;
        this.inserter = inserter;
    }


    @Override
    public EntityResponse.Builder<T> status(HttpStatus status) {
        Assert.notNull(status, "HttpStatus must not be null");
        this.status = status.value();
        return this;
    }

    @Override
    public EntityResponse.Builder<T> status(int status) {
        this.status = status;
        return this;
    }

    @Override
    public EntityResponse.Builder<T> cookie(ResponseCookie cookie) {
        Assert.notNull(cookie, "ResponseCookie must not be null");
        this.cookies.add(cookie.getName(), cookie);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> cookies(Consumer<MultiValueMap<String, ResponseCookie>> cookiesConsumer) {
        Assert.notNull(cookiesConsumer, "Consumer must not be null");
        cookiesConsumer.accept(this.cookies);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> header(String headerName, String... headerValues) {
        for (String headerValue : headerValues) {
            this.headers.add(headerName, headerValue);
        }
        return this;
    }

    @Override
    public EntityResponse.Builder<T> headers(HttpHeaders headers) {
        this.headers.putAll(headers);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> allow(HttpMethod... allowedMethods) {
        this.headers.setAllow(new LinkedHashSet<>(Arrays.asList(allowedMethods)));
        return this;
    }

    @Override
    public EntityResponse.Builder<T> allow(Set<HttpMethod> allowedMethods) {
        this.headers.setAllow(allowedMethods);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> contentLength(long contentLength) {
        this.headers.setContentLength(contentLength);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> contentType(MediaType contentType) {
        this.headers.setContentType(contentType);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> eTag(String etag) {
        if (!etag.startsWith("\"") && !etag.startsWith("W/\"")) {
            etag = "\"" + etag;
        }
        if (!etag.endsWith("\"")) {
            etag = etag + "\"";
        }
        this.headers.setETag(etag);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> hint(String key, Object value) {
        this.hints.put(key, value);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> lastModified(ZonedDateTime lastModified) {
        ZonedDateTime gmt = lastModified.withZoneSameInstant(ZoneId.of("GMT"));
        String headerValue = DateTimeFormatter.RFC_1123_DATE_TIME.format(gmt);
        this.headers.set(HttpHeaders.LAST_MODIFIED, headerValue);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> location(URI location) {
        this.headers.setLocation(location);
        return this;
    }

    @Override
    public EntityResponse.Builder<T> cacheControl(CacheControl cacheControl) {
        String ccValue = cacheControl.getHeaderValue();
        if (ccValue != null) {
            this.headers.setCacheControl(cacheControl.getHeaderValue());
        }
        return this;
    }

    @Override
    public EntityResponse.Builder<T> varyBy(String... requestHeaders) {
        this.headers.setVary(Arrays.asList(requestHeaders));
        return this;
    }

    @Override
    public Mono<EntityResponse<T>> build() {
        return Mono.just(new DefaultEntityResponse<T>(
                this.status, this.headers, this.cookies, this.entity, this.inserter, this.hints));
    }


    private final static class DefaultEntityResponse<T>
            extends DefaultServerResponseBuilder.AbstractServerResponse
            implements EntityResponse<T> {

        private final T entity;

        private final BodyInserter<T, ? super ServerHttpResponse> inserter;

        private final Map<String, Object> hints;

        public DefaultEntityResponse(int statusCode, HttpHeaders headers,
                                     MultiValueMap<String, ResponseCookie> cookies, T entity,
                                     BodyInserter<T, ? super ServerHttpResponse> inserter, Map<String, Object> hints) {

            super(statusCode, headers, cookies);
            this.entity = entity;
            this.inserter = inserter;
            this.hints = hints;
        }

        @Override
        public T entity() {
            return this.entity;
        }

        @Override
        public BodyInserter<T, ? super ServerHttpResponse> inserter() {
            return this.inserter;
        }

        @Override
        protected Mono<Void> writeToInternal(ServerWebExchange exchange, Context context) {
            return inserter().insert(exchange.getResponse(), new BodyInserter.Context() {
                @Override
                public List<HttpMessageWriter<?>> messageWriters() {
                    return context.messageWriters();
                }

                @Override
                public Optional<ServerHttpRequest> serverRequest() {
                    return Optional.of(exchange.getRequest());
                }

                @Override
                public Map<String, Object> hints() {
                    return hints;
                }
            });
        }
    }

}
